1. Field of the Invention
The present invention relates to a car navigation apparatus which can always detect a position of a car with high accuracy, a car navigation apparatus which can obtain traffic information in a practical manner, a traffic information providing apparatus for providing a car navigation apparatus with traffic information in a practical manner, and program recording media for realizing those apparatuses.
2. Description of Related Art
Generally, a car navigation apparatus detects a position of a car by the use of the GPS (Global Positioning System). The car position data detected by the GPS has some errors due to environmental conditions.
So, the DGPS (differential GPS) which improves the accuracy of measuring a position of a car is used. In the DGPS, a base station (FM broadcasting station etc.) which has obtained data of a correct car position in advance measures a car position using the GPS, and transmits the difference therebetween to the car as correction data. Then, the car position measured by the car using the GPS is corrected by using the transmitted correction data.
Conventionally, the correction data of the DGPS (the correction data used in the DGPS) is transmitted by the FM multiplex broadcasting.
So, the conventional car navigation apparatus obtains the DGPS correction data by receiving the FM broadcasting and decodes DGPS signals multiplexed into the FM broadcasting to convert the DGPS signals to the DGPS correction data.
On the other hand, systems for providing a car navigation apparatus with traffic information such as the VICS (Vehicle Information and Communication System) come into practical use.
The traffic information providing system such as the VICS transmits traffic information such as traffic congestions, traffic accidents, traffic regulations and parking lots by the FM multiplex broadcasting.
So, the conventional car navigation apparatus obtains the traffic information such as traffic congestions, traffic accidents, traffic regulations and parking lots and outputs the traffic information by receiving the FM broadcasting and decodes the VICS signals multiplexed into the FM broadcasting to convert the VICS signals to character data. On the other hand, the traffic information can be obtained from beacons (information communication terminals) disposed on roads.
In this way, the conventional car navigation apparatus obtains the DGPS correction data and traffic information by receiving the FM broadcasting.
However, in obtaining the DGPS correction data by receiving the FM broadcasting, in case the car navigation apparatus is distant from the FM broadcasting stations (which are limited in number) or the state of radio waves of the FM broadcasting is deteriorated, it becomes difficult to obtain the DGPS correction data or it takes a considerably long time before the DGPS correction data has been received.
So, the DGPS sometimes does not work, which deteriorates the measurement accuracy.
Also, in case the car navigation apparatus is distant from the FM broadcasting stations, only the DGPS correction data of distant FM broadcasting stations can be obtained, which can not perform correcting operation with accuracy.
Furthermore, in obtaining the traffic information by receiving the FM broadcasting, in case the car navigation apparatus is distant from the FM broadcasting stations (which are limited in number) or the state of radio waves of the FM broadcasting is deteriorated, it becomes difficult to obtain the traffic information or it takes a considerably long time before the traffic information has been received.
So, sometimes the necessary traffic information cannot be obtained when required.
Furthermore, in obtaining the traffic information by receiving the FM broadcasting, since the traffic information is transmitted in one-way radio communication or the traffic information is transmitted only from the FM broadcasting stations, the desired traffic information cannot be obtained selectively or according to the priority.
It is therefore an object of the present invention to overcome the above-mentioned drawbacks by providing a new car navigation apparatus which can always detect a position of a car with high accuracy, a new car navigation apparatus which can obtain traffic information in a practical manner, a new traffic information providing apparatus for providing a car navigation apparatus with traffic information in a practical manner, and new program recording media for realizing those apparatuses.
According to the present invention, there is provided a car navigation apparatus that detects and corrects a current position of a motor vehicle by the use of radio communication. A preliminary current position of the vehicle is detected. At least one base station is detected out of base stations near the detected preliminary current position of the vehicle using information of positions of a plurality of base stations which have been registered in map data in advance. A correction data request is transmitted to the detected base station. Correction data is transmitted from the detected base station in response to the request, received by the navigation apparatus, and a corrected current position of the vehicle is corrected by correcting the preliminary current position using the received correction data.
Specifically, the function of the car navigation apparatus can be realized by executing a program, and the program can be stored in an appropriate recording medium such as a semiconductor memory whose data can be read out by a computer.
The car navigation apparatus obtains the correction data for use in correcting the position information detected using the radio determination from a base station which is nearest the car in two-way radio communication, and corrects the current position information detected using the radio determination.
Thus, the car navigation apparatus according to the present invention obtains the DGPS correction data from a base station nearest the car in two-way radio communication instead of obtaining the DGPS correction data by receiving the FM broadcasting. So, the car navigation apparatus can promptly obtain the DGPS correction data when necessary, which is capable of correcting a car position with high accuracy. Accordingly, the current position of the car can always be detected with high accuracy.
Furthermore, according to the present invention, there is provided a car navigation apparatus, including:
means for detecting current position information of a car by the use of the radio determination;
means for setting up destination information and/or route information to the destination;
means for designating the current position information detected by the detecting means and/or the set up information set up by the setting up means, and transmitting traffic information providing request to an external traffic information providing system;
means for receiving traffic information transmitted in response to the traffic information providing request from the traffic information providing system; and
means for outputting the received traffic information.
Furthermore, according to the present invention, there is provided a traffic information providing apparatus, including:
means for storing traffic information to be presented to a car navigation apparatus;
means for receiving traffic information providing request from the car navigation apparatus, the traffic information providing request being issued when at least a piece of information among current position information of a car, destination information, and route information to the destination is designated;
means for extracting only traffic information highly associated with the information designated by the traffic information providing request from the traffic information to be presented to the car navigation apparatus, or deciding the priority of the traffic information to be presented to the car navigation apparatus in accordance with degree of association with the designated information; and
means for transmitting the extracted traffic information, or transmitting the traffic information in accordance with order of the priority to the car navigation apparatus which issued the traffic information providing request.
Specifically, the function of the car navigation apparatus and traffic information providing apparatus can be realized by executing a program, and the program can be stored in an appropriate recording medium such as a semiconductor memory whose data can be read out by a computer.
In the car navigation system according to the present invention, the car navigation apparatus according to the present invention designates at least a piece of information among current position information of a car, destination information, and route information to the destination, and issues the traffic information providing request to the traffic information providing apparatus in two-way radio communication. On receiving the traffic information providing request, the traffic information providing apparatus according to the present invention returns only traffic information highly associated with the information designated by the traffic information providing request, or returns traffic information in order of the priority in accordance with degree of association with the information designated by the traffic information providing request to the car navigation apparatus which issued the traffic information providing request.
Thus, the car navigation apparatus according to the present invention obtains traffic information by having access to a traffic information providing system in two-way radio communication instead of obtaining traffic information by receiving the FM broadcasting. So, the car navigation apparatus can promptly obtain traffic information when necessary.
Furthermore, with the traffic information providing apparatus according to the present invention being provided, the car navigation apparatus according to the present invention can obtain necessary traffic information promptly since the car navigation apparatus can obtain traffic information selectively or according to the priority in accordance with circumstances a car is facing.
These objects and other objects, features and advantages of the present invention will become more apparent from the following detailed description of the preferred embodiments of the present invention when taken in conjunction with the accompanying drawings.